Method for fabricating a local interconnection structure

Abstract

A local interconnection structure is disclosed. The local interconnection structure is formed on a silicon substrate in which a polysilicon gate and a number of diffusion regions exist. The structure includes a number of metal silicide layers over the substrate, a metal nitride layer over the silicide layers, and a dielectric layer over the nitride layer. The metal nitride layer which electrically connects the diffusion regions and the gate forms the interconnection. The method for fabricating the interconnection structure includes the steps of preparing the silicon substrate, sputtering a metal layer, annealing to form silicide and the nitride layers, depositing the dielectric layer, and patterning the nitride layer and the metal nitride by covering with a mask, etching away portions of both the dielectric layer and metal nitride layer not covered by the mask, and removing the mask after etching.

What is claimed is: 
     
       1. A method for fabricating a local interconnection structure on a silicon substrate which has a plurality of diffusion regions and a polysilicon gate, said method comprising: forming a metal layer over said silicon substrate;   heating said metal layer and said silicon substrate in a nitrogen-containing atmosphere to form silicide layers over said polysilicon gates and said diffusion regions and to form a metal nitride layer over said silicon substrate;   forming a dielectric layer over said metal nitride layer; and   patterning said dielectric layer and said metal nitride layer to form said local interconnection structure by covering with a mask said local interconnection structure to be formed and etching away portions of both said dielectric layer and said metal nitride layer not covered by said mask and removing said mask after said etching.   
     
     
       2. The method as claimed in claim 1, wherein said metal layer is formed by sputtering a titanium layer. 
     
     
       3. The method as claimed in claim 1, wherein said metal layer is heated by a rapid thermal process. 
     
     
       4. The method as claimed in claim 1, wherein said dielectric layer is formed by depositing a silicon dioxide layer. 
     
     
       5. The method as claimed in claim 1, wherein said dielectric layer is formed by depositing a silicon nitride layer. 
     
     
       6. The method as claimed in claim 1 further comprising: forming a polysilicon layer over said substrate to define a contact window region before the formation of said metal layer.   
     
     
       7. The method as claimed in claim 6 further comprising: forming a passivation layer over said local interconnection structure;   forming a contact window over said contact window region through said passivation layer and said dielectric layer; and   forming a metal line over said passivation layer which extends through said contact window to contact said metal nitride layer.   
     
     
       8. The method as claimed in claim 1 wherein said step of patterning is performed by reactive ion etching. 
     
     
       9. The method as claimed in claim 1 wherein said mask comprises photoresist.